Excitation frequency dependence and fluorescence in the Raman spectra of Al2O3

Raman spectra of aluminum oxide, Al2O3, have been a subject of interest over the last two decades. The origin of the fluorescence background in the Raman spectra of Al2O3 is still a subject of discussion. It has been believed to be due to hydrocarbon, iron ion impurities, or hydroxy groups on the surface of Al2O3. In this paper, Raman spectra of Al2O3 are reported that were acquired with different excitation frequencies as well as different spectrometers and different temperatures. It is shown that, whereas at an excitation frequency of 1064 nm a strong fluorescence background is observed, a sample of Al2O3 heated at 1250 degrees C when excited with a 632.8-nm frequency exhibits strong and remarkable fluorescence fine structure. It is concluded that the origin of the fluorescence background in the Raman spectra of Al2O3 is iron, and Fe impurity, and the intensity of this fluorescence depends upon the structure of Al2O3 and the excitation frequency used.